It is 4pm in Emma Freud's Notting Hill work studio and I am with a bunch of famous show-offs including Edith Bowman, Stephen Mangan, Katy Brand and Dan "Downton Abbey" Stevens, who are loudly massacring the Shipping Forecast theme tune. On kazoos.

This group is a fraction of the 87-strong (and counting) Comic Relief celebrity kazoo orchestra which on Monday will perform The Ride of the Valkyries and the Dambusters Theme in The Big Red Nose Show at the Royal Albert Hall.

The audience - who will also get to hear some proper classical music from the likes of violinist Nicola Benedetti, cellist Julian Lloyd Webber and the BBC Concert Orchestra conducted by Sue Perkins - will all be supplied with kazoos and encouraged to join in.

If the hall is filled to its 5,435 capacity, the Guinness World Record for the largest kazoo ensemble - currently held by 3,861 Australians - will be smashed. The whole concert will be compered by Katie Derham and Basil Brush, and broadcast on Radio 3 on Red Nose Day, Friday March 18.

So the cost of a ticket is a double guarantee of immortality, in the record books and the BBC archives. It will also be a chance to witness something funny, unique and incredibly loud. And utterly shambolic, if the sneak preview I'm taking part in is anything to go by.

We have been assembled by Freud and her Comic Relief cohort Emma Kennedy to record idents for BBC Radio to broadcast in the run-up to Red Nose Day. Our confused Sailing By will precede John Prescott reading the Shipping Forecast on Radio 4. We're slightly better with the Archers theme, much worse on the Radio 2 jingle, even though it's only seven notes long. "Well, we all finished on the same note," says Freud, looking on the bright side.

"Someone from Comic Relief rang me and said, Radio 3 are very keen on us this year, they've booked the Albert Hall," she recalls. "We loved the idea of marrying what we do in comedy with what they do with classical music. The original plan was to have just a few kazooers on stage but I mentioned it to Kennedy and suddenly there were 87."

Those taking part include Al Murray, Miranda Hart, Krishnan Guru-Murthy, Gaby Roslin, Richard Bacon and Tracy-Ann Oberman. And me. Within seconds in their company I have been co-opted by Freud and Kennedy. And there are more joining all the time.

"It's the relentless bullying of the double-headed 'Emma hydra' that brings these things together," jokes Brand. "Actually, an event like this is a no-brainer, because it's fun, it's for charity, and you get to hang out with a lot of mates."

Edith Bowman points out that it's also a chance to play the Albert Hall, which she might find scary under other circumstances. Broadcaster Sarah Cawood, who is 5ft 1in, is planning to stand next to the 6ft 1in Miranda Hart for comedy purposes. Stevens and Mangan are competing to get the deepest notes out of their kazoos.

Both Emmas say it has become progressively easier each year to get people to perform for Comic Relief, which was founded in 1986 by Freud's partner, screenwriter Richard Curtis. "It's an easy ask these days because the Comic Relief community has got bigger and bigger," says Kennedy. Columnist Caitlin Moran chips in: "And because I emailed everyone after you and said we'd all be going to the pub afterwards."

As if to underline the level of enthusiasm, comedian Shappi Khorsandi, who couldn't make the preliminary session, rings in. Turns out she was in such a rush to join the kazooers, she didn't check what songs she'd be playing. "I've been practising My Old Man's a Dustman and It's a Long Way to Tipperary," she wails.

At the Albert Hall, the Comic Relief crowd will be led by professional group Masters of the Kazooniverse but there won't be time for formal rehearsals. "I imagine we'll have a buzz-through backstage," says Kennedy. "And I'm sure we'll be absolutely fine on the night."

Hmm. Perhaps. As we assemble for photos on the stairs, a reedy, rackety version of The Wizard of Oz starts up. We're getting better, I think. A bit. So buy a ticket, come along, join in. I can't guarantee we'll be tuneful. But I can guarantee we will be funny.